CDMA 原理原理1 1 主要主要内容内容码分多址的基本原理码分多址的关键技术CDMA同GSM的比较2 2 目标不同用户是如何用码区分出来的三种CDMA码的用途CDMA逻辑信道的划分编码，软切换和功率控制3 3 码分多址的基本原理码分多址的关键技术CDMA同GSM的比较4 4 N Users / Wideband Channel C/I is still negative after I.F. filtering but positive after despreading process Can consider despreading as the last filtering stage 3 Users / Narrowband Channel C/I is negative prior to I.F. filtering and positive after filtering1231TDMA (3 timeslots shown)30 kHzFrequencyTime 1 User/ Narrowband Channel C/I is negative prior to I.F. filtering and positive after filteringFDMA30 kHzFrequencyTimeDS-CDMA1.23 MHzFrequencyTime CDMACDMA基本原理基本原理Walsh Code5 5 IS-95 was an interim standard developed by TIA/EIA. IS-95 defined mobile station and base station compatibility for the first application of CDMA technology in cellular systems.TIA/EIA is an accredited standards development organization through the ANSITIA/EIA: Telecommunications Industries Association/Electronics Industries AssociationANSI: American National Standards InstituteIS-95接口标准接口标准6 6 MSCCBSCPSTNBTSCDMA系统网络结构系统网络结构7 7 BTSBTSCBSCCBSCCDMACDMA IS-95IS-95A+A+系统结构实系统结构实例例 开放的网结构开放的网结构Opening Network Opening Network ArchitectureArchitectureCDG IOSCDG IOSCell SiteCell SiteVoiceVoiceControlControlLInterfaceUNOUNOOMC- ROMC- RBTSBTSBTSBTSXCIWUMMMSC/VLRMSC/VLR CDG IOSCDG IOSPSTNPSTNPSTNPSTNIN ApplicationHLRMSCSMSVMSANSI-41ANSI-418 8 CDMA 物理信道物理信道 Tx: 870-880MHzRx: 825-835MHz9 9 CDMA 首选载波分配首选载波分配System DesignatorPreferred Set Channel NumbersA283(Primary) 691(Secondary)B384(Primary)777(Secondary)1010 联通拥有的频率资源联通拥有的频率资源825835845CDMA Tx870880CDMA Rx960 CDMA/AMPSUC CDMASpectrum Allocation GSM Rx915 GSM TxFreq(MHz)CMCC GSM935890909UC GSMUCUC954A Band B BandA Band B BandCMCC894CMCC9391111 CDMA的基本原理：CDMA码PN码 （伪随机噪声序列）貌似随机，实际上是有规律的周期性二进制序列。在CDMA中用到两个伪随机序列，长码和短码。Walsh Code具有正交特性1212 伪随机码伪随机码 (PN CODE) 的生成的生成0100011100401021015110611170113001114256731313 010001110041106111701131015010200111467352伪随机码伪随机码 (PN CODE)1414 Walsh码递归公式码递归公式1515 8阶阶Walsh码码W00 0 0 0 0 0 0 0W10 1 0 1 0 1 0 1W20 0 1 1 0 0 1 1W30 1 1 0 0 1 1 0W40 0 0 0 1 1 1 1W50 1 0 1 1 0 1 0W60 0 1 1 1 1 0 0W70 1 1 0 1 0 0 11616 CDMA CodesPN short codeLength215 1 1 215 32，768 chipsWalsh code64 PN long codeLength242-1 4.4 1012 chips1717 CDMA系统中采用的编码系统中采用的编码Walsh Walsh 码码码码 在在CDMA前向逻辑信道中使用前向逻辑信道中使用,以区分同一小区或扇区以区分同一小区或扇区 用户用户1818 PN PN 短码短码短码短码 区分不同扇区或小区 伪随机序列 215 = 32,768 unit (period 26.67ms) 用于前向及反向物理信道扩频CDMA系统中采用的编码系统中采用的编码1919 64 chips32,768 chips / 64 = 512 PN offsets.PN chipsPN短码偏置短码偏置2020 长码长码长码长码 用于反向逻辑信道区分不同用户 伪随机序列 242-1 unit 在前向链路上对业务及寻呼信道进行扰码CDMA系统中采用的编码系统中采用的编码2121 CDMA前向信道结构前向信道结构2222 CDMA反向信道结构反向信道结构2323 CDMACDMA前向信道结构前向信道结构前向信道结构前向信道结构2424 CDMACDMA前向信道结构前向信道结构前向信道结构前向信道结构2525 CDMACDMA反向信道结构反向信道结构反向信道结构反向信道结构2626 CDMACDMA反向信道结构反向信道结构反向信道结构反向信道结构2727 Overhead Channels Traffic ChannelsCarry messaging,Identification and Primarily carry voice and user data timing information traffic Carry some signaling informationused to control MSPilotSyncForward Forward TrafficPagingAccessReverse Reverse TrafficCDMA基本原理基本原理2828 PilotSyncPagingTrafficDSS by Walsh 0DSS by Walsh 32DSS by Walsh 1-7DSS by remaining 55Walsh codes64 logical channelsare combinedThen quadraturespread using pilotPN codeCDMA基本原理基本原理2929 Spread by long code(offset)Spread by long code(offset)Access TrafficQuadrature spread usingpilot PN code withoutany offsetCDMA基本原理基本原理3030 码分多址的基本原理码分多址的关键技术CDMA同GSM的比较3131 码激励线性预测编码码激励线性预测编码(CELP) 功率控制功率控制软切换软切换CDMA关键技术关键技术3232 CELPCode Excited Linear PredictiveCompressed digital voice between XC and MSUses much less data to approximate the original signal8K or 13K3333 功率控制功率控制反向开环功率控制反向闭环功率控制前向闭环功率控制3434 功率控制的重要性功率控制的重要性3535 ForwardReverse远近效应远近效应远近效应远近效应功率控制功率控制Based on:Based on:power measurement (power measurement (EbEb/No)/No)frame error rate(FER)frame error rate(FER)3636 TimeAccess ProbesInitialPowerInitial Power+open loop correctionTx Power(dbm)开环功率控制开环功率控制3737 开环功率控制开环功率控制：Assumes Loss is Similar on Forward and Reverse PathsReceive Power+Transmit Power = -73All powers in dBmExample:For a Received Power of -85 dBm Transmit Power = (-73) - (-85) Transmit Power = +12 dBmProvides an Estimate of Reverse TX Power for Given Propagation Conditions3838 反向功率控制反向功率控制：Maximum System Capacity is Achieved if:All Mobiles are Powered Controlled to the Minimum Power for Acceptable Signal QualityAs a result, all Mobiles are Received at About Equal Power at the Base Station Independent of Their LocationThere are Two Types of Reverse Control:Open Loop Power ControlClosed Loop Power ControlOpen & Closed Loop Power Control are Always Both Active 3939 闭环功率控制闭环功率控制：Directed by Base StationUpdated Every 1.25 msecCommands Mobile to Change TX Power in +/-1 dB Step SizeFine Tunes Open Loop Power EstimatePower Control Bits are Punctured over the Encoded Voice DataPuncture Period is two 19.2 kbps Symbol Periods = 103.6 usec 4040 FDMA & TDMA FDMA & TDMA 切换切换切换切换Break-before-make4141 CDMA软切换软切换Make-before-break4242 CDMA软切换软切换更软切换软切换CBSC 间软切换4343 Narrow BandCellsCompeteHardHand-OffMobile PositionCellACellBSoftHandoffSignal StrengthABCDMACellsTeam upSoftHand-OffBreak Before MakeMake Before Break 软切换软切换软切换软切换4444 软切换导频集软切换导频集软切换导频集软切换导频集ActiveActiveActiveNeighborNeighborNeighborNeighborNeighborNeighborNeighborRemainingRemaining 有效导频集有效导频集有效导频集有效导频集 相邻导频集相邻导频集相邻导频集相邻导频集 剩余导频集剩余导频集剩余导频集剩余导频集 候选导频集候选导频集候选导频集候选导频集4545 软切换软切换软切换软切换Threshold &Threshold &TimerTimerT-AddT-AddT-CompT-CompT-DropT-DropT-TdropT-TdropSearch, compare, combine, then Soft handoffSearch, compare, combine, then Soft handoff4646 软切换参数软切换参数软切换参数软切换参数Pilot StrengthT-CompT-AddT-dropT-TdropTimeActive PilotNeighbor or RemainingNeighborActiveCandidate4747 分集技术：分集技术：信号元素合并(Rake 接收机)帧选择4848 Rake接收机接收机4949 Path Diversity Improves Voice QualityPath Diversity Improves Voice QualityReceiverReceiverReceiverMobile Rake ReceiverAnalogTDMACalls FadingD/AAudio FadingD/AMobileReceiverCDMA CallsEffects of fading are mitigated through use of multiple receivers that sum radio signals from different cells and from reflected rays. Fading is more likely to cause loss of information = lower speech quality5050 Soft Handoff Improves Voice QualitySoft Handoff Improves Voice QualityMultiple receive pathsSwitchFrame Quality IndicatorQualityFramesFrame Quality IndicatorQualityFramesQualityFramesImproved Speech QualityTranscoder picks best frame from up to three soft handoff cells.CDMA Soft Handoff Improves Frame Quality43214321seven frames shown in this example1234 56711223344556677Chosen frames of Transcoder5151 Frequency Diversity Improves Voice QualityFrequency Diversity Improves Voice QualityOutgoing Waveform-80 dB-90 db-110 db-120 db1.25 Mhz1.25 MhzThis 400 Khz fade of 12 db only affects 1/3 of CDMA bandwidth.Therefore, total fade to CDMA user is 2 dbThe entire 30 KHz Channel of TDMA is affected by this same fade. Therefore, total fade to end user is 12 db.CDMA Offers More Protection Against Frequency Selective FadingReceived Waveform-80 db-90 db-110 db-120 db30 KhzOutgoing Waveform-80 db-90 db-110 db-120 db30 KhzReceived Waveform-80 db-90 db-110 db-120 db12 dB Fade2 dB Loss12 dB Fade12 dB Loss!CDMATDMA5252 码分多址的基本原理码分多址的关键技术CDMA同GSM的比较5353 Cdma2000 1X 技术特点技术特点Motorola cdma2000 1X 网络结构网络结构5959 cdma20001X 技术特点技术特点6060 Performance EnhancementsReverse Link Pilot for Each MobileTrue QPSK ModulationContinuous Reverse Link WaveformImproved Convolutional Encoding for 14.4 kbps Voice ChannelsFast Forward & Reverse Link Power ControlSupports Auxiliary Pilots for Beam FormingForward Link Transmit Diversity - OTD, Multi-Antennacdma20006161 Reuse of TIA/EIA-95-Bcdma2000 is Fully Backwards Compatible with TIA/EIA-95-BReused Aspects of TIA/EIA-95-B:TIA/EIA-95-B Radio InterfaceIS-707 Data ServicesIS-127 EVRC 8 kbps Vocoder and IS-733 13 kbps VocoderIS-637 SMS & IS-683 Over the Air ActivationIS-98 and IS-97 Minimum Performance StandardsCommon Broadcast Channels (Pilot, Sync Paging)Allows cdma2000 to be Deployed Sooner6262 cdma2000 Terms & DefinitionsChipA chip is a data bit at the final spreading rateSR - Spreading RateDefines the final spreading rate in terms of 1.2288 Mcps. So a 3.6864 Mcps system is called a SR3 system.RC - Radio ConfigurationDefines the physical channel configuration based upon a base channel data rate.RCs contain rates derived from their base rate. For example, RC3 is based on 9.6 kbps and includes 1.5, 2.7, 4.8, 9.6, 19.2, 38.4, 76.8, 153.6, and 307.200 kbps.RCs are coupled to specific Spreading Rates6363 cdma2000 SR1Is an Improved TIA/EIA-95-B Narrowband SystemOccupies the Same 1.23 MHz Bandwidth as TIA/EIA-95-BForward Link:Adds Fast Power ControlUses QPSK Modulation Rather than Dual BPSK to:Use 3/8 Rate Convolutional Encoder instead of 3/4 for 14.4 Service (improves error correction) 128 Walsh Codes to Handle More Soft Handoffs for 9.6 serviceReverse Link:Uses Pilot Aided BPSK to Allow Coherent DemodulationUses 1/4 Rate Convolutional Encode Instead of 1/2 or 1/3Uses HPSK SpreadingEnhance System Capacity6464 cdma2000 1X 要点要点技术改善技术改善对数据应用支持 MAC, QoS, 和turbo码快速前后向功率控制反向信道相干解调后向兼容 IS-95A/BOperator Benefits可支持高达153.6k bps数据速率与IS-95A/B相比，数据应用能力有4-6倍的提高 与IS-95A/B相比， 话音容量有1.5-1.8倍的提高，减小了运营成本在保护IS-95A/B投资的前提下，提供了经济有效的过渡策略6565 CDMA2000 1x 原理原理可变长度的可变长度的 Walsh Code 码码6666 Walsh Code Length v.s Data RateEncoderRate = rInterleaverRepetitionFactor = R+A(t)Walsh code (Length WL)at 1.2288mcpsData RateCoded SymbolsRepeated SymbolsModulation SymbolsA(t)=d(t)/r*R*WLWL=1228800*r/d(t)/R6767 W080 0 0 0 0 0 0 0W180 1 0 1 0 1 0 1W280 0 1 1 0 0 1 1W380 1 1 0 0 1 1 0W480 0 0 0 1 1 1 1W580 1 0 1 1 0 1 0W680 0 1 1 1 1 0 0W780 1 1 0 1 0 0 1Walsh Code:Generation & Use in 95A/B6868 Walsh Code:Generation & Use in CDMA2000W01 =0W02 =00W12 =01W04 =0000W24 =0011W14 =0101W34 =0110W08 =00000000W48 =00001111W28 =00110011W68 =00111100W18 =01010101W58 =01011010W38 =01100110W78 =01101001( W016 ,W816)( W416 ,W1216 )( W216 ,W1416 )( W616 ,W1416 )( W116 ,W916 )( W516 ,W1316 )( W316 ,W1116 )( W716 ,W1516 )SF=1SF=2SF=4SF=8SF=166969 Effects of Using Variable Length Walsh Codes for SpreadingSF=16SF=2SF=4SF=81 1 1 1 1 1 1 11 1 1 1 -1 -1 -1 -11 1 -1 -11 1 1 11 1 1 -1 1 -1 1 -11 -1 -1 11 1 -1 1 -1 1 -1 1 -11 -1 1 -1 -1 1 -1 11 -1 -1 1 1 -1 -1 11 -1 -1 1 -1 1 1 -11 1 -1 -1 -1 -1 1 11 1 -1 -1 1 1 -1 -11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 -1 -1 -1 -1 -1 -1 -1 -11 1 1 1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 -11 1 1 1 -1 -1 -1 -1 -1 -1 -1 -1 1 1 1 1Using Shorter Walsh Codes Precludes Using all Longer Codes Derived from the OriginalShorter Codes on a Branch map into Longer Codes1 1 -1 -1 1 1 -1 -1 1 1 -1 -1 1 1 -1 -11 1 -1 -1 1 1 -1 -1 -1 -1 1 1 -1 -1 1 11 1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 -1 1 11 1 -1 -1 -1 -1 1 1 -1 -1 1 1 1 1 -1 -11 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -11 -1 1 -1 1 -1 1 -1 -1 1 -1 1 -1 1 -1 11 -1 1 -1 -1 1 -1 1 1 -1 1 -1 -1 1 -1 11 -1 1 -1 -1 1 -1 1 -1 1 -1 1 1 -1 1 -11 -1 -1 1 1 -1 -1 1 1 -1 -1 1 1 -1 -1 11 -1 -1 1 1 -1 -1 1 -1 1 1 -1 -1 1 1 -11 -1 -1 1 -1 1 1 -1 1 -1 -1 1 -1 1 1 -11 -1 -1 1 -1 1 1 -1 -1 1 1 -1 1 -1 -1 17070 64481632129600192003840076800153600 307200 614400Data rate -bps-Walsh Code Length -chips-Walsh Code Length v.s Data Rate7171 Long CodeGeneratorBitSelector(Decimator)MUXand SignalPointMapping0 - +11 - -1PCChannelGainDataChannelGainDataChannelGainPuncturePC Sym.(optional)PuncturePC Sym.(optional)WalshCodeYqYiMUX ControlIQAds (t) ds1 (t) Wi (t) ds2 (t) j Wi (t) ds1 (t) ds2 (t) PC Bits800 bps+ or - ValuesFrom InterleaverComplex Walsh Covering7272 XYComplex PN CodePN(t) 1+ jX .PN i(t)PNi (t)jPNq (t)X . j .PN q(t)= ds1 (t) Wi (t). PN i(t)= ds1 (t) Wi (t). j .PNq(t)Complex PN CodePN(t) 1+ jS2Z1Y . j .PN q(t)= ds2 (t) j Wi (t). j .PNq(t) jPNq (t)S3S0S1Y .PN i(t) = ds2 (t) j Wi (t). PN i(t)PNi (t)S2S0S3S1Complex PN Spreading and MappingRealSumImagSumZo7373 CDMA2000 1x 原理原理CDMA2000 1x 前反向信道结构前反向信道结构7474 FLSR1/3CommonAssignmentCommonPower ControlPilotCommonControlSyncTrafficBroadcastPaging(SR1)QuickPagingF- PilotTransmitDiversity PilotAuxiliaryPilotAuxiliary TransmitDiversity Pilot0-1 DedicatedControl0-1 FundamentalPower Control/Reverse Pilot0-7 Supplemental CodeRC 1-20-2 Supplemental CodeRC 3-9CDMA2000 Forward Link Channels7575 Tx Data Rates (bps)20msFrameRC1RC2RC3RC4RC51200307200153600768003840019200960048002400Rate Set 1 “derived”Walsh CodesW n 256W n 04W n 08W n 16W n 32W n 64W n 128W n 128W n 128r = 1/2r =1/2r = 1/2r = 1/4r = 1/4F-SCH Walsh Codes vs Data Rates for Radio Configuration 37676 Tx Data Rates (bps)20msFrameRC1RC2RC3RC4RC51200307200153600768003840019200960048002400Rate Set 1 “derived”Walsh CodesW n 256W n 04W n 08W n 16W n 32W n 64W n 128W n 128W n 128r = 1/2r =1/2r = 1/2r = 1/4r = 1/4F-SCH Walsh Codes vs Data Rates for Radio Configuration 47777 RLSR1/3AccessR-TCHRC 1/2Enhanced AccessCh OperationR-Common ControlCh OperationR-TCH OperationRC 3-6R-FCH0-7 R-SCCHR-Pilot ChEnhanced AccessR-Pilot ChR-CCCHR-Pilot Ch0-1 R-DCCH0-1 R-FCH0-2 R-SCHR-Power ControlSubChCDMA2000 Reverse Link Channels7878 MUXPilot (all 0s)PC BitsPC BitsPilot (all 0s)384 chips1 PCG = 4x384 chips = 1536 chipsAPC BitsPilot (all 0s)Reverse Pilot Channel with Reverse PC subchannel7979 Reverse Link Frame =20ms=16PCGs01234567891011121314151 PCG PC sub-channel Reverse Pilot CHStructure of Pilot Symbols and Power Control Bits8080 +PNQ PN I +PN I PN QWalsh Codes-Variable Length R-DCCHAR-PICH XCRelativeGainR-SCH2RelativeGainXBI - dataQ - dataXSin (2 ft + )BBFCos(2 ft + )BBFXWalsh Codes-Variable Length RelativeGainXCR-FCH RelativeGainXCR-SCH1 R-EACHR-CCCH8181 CDMA2000 1x 原理原理增强型软切换增强型软切换8282 CellACellBSoftHandoffSignal StrengthABT1T2M1M28383 CDMA2000 1x 原理原理CDMA2000 OSI结构结构8484 LinkLayer (OSI 2)UpperLayers (OSI 3-7)PhysicalLayer (OSI 1)Unique to cdma20008585 LAC functionLength and CRC FieldsEncapsulated LAC-PDULAC-PDU FragmentsSARSARSAR9108FieldsLAC-PDU (Non-encapsulated)Sub-LayersIllustrationMessage type FieldsUtility5ARQ FieldsARQ3Addressing FieldsAddressing4Authentication FieldsAuthentication2SDU BODY Fields + MCSBLayer 3 SDU1Pilot Measurement Report FieldsUtility6LAC-PDU Padding FieldsUtility78686 CDMA Technology EvolutionIS-95AIS-95Bcdma2000 1XVoice Cap=15.5E/sector100% 8k voiceAvg sect throughput=75 KbpsPeak Data Rate=14.4 KbpsVoice Cap=15.5E/sector100% 8k EVRC voiceAvg sect throughput=75 KbpsPeak Data Rate=64 Kbps1xEV-DO1xEV-DVVoice Cap=23.3E/sector w/TD100% 8k EVRC voiceAvg sect throughput=340 Kbps w/TDPeak Data Rate=614 KbpsNo VoiceAvg sect throughput=620 KbpsPeak Data Rate=2.4 MbpsVoice Cap=23.3E/sector w/TD100% 8k EVRC voiceAvg sect throughput=1.2 Mbps w/TDPeak Data Rate=5 Mbps1995199920012002200320048787 cdma2000 1X 网络结构网络结构8888 AAAPDSN1X BTS1X BTSTo PSTNHAMSC/HLRTo Packet Data NetworkCBSC/ANCircuit LinkPacket Linkcdma2000 1X系统功能框图系统功能框图IP8989 cost savings% of system using 1X 中低速数据的部署: 低话务区 (郊县/农村)中低速数据的要求 (14.4 - 64kbps)优势优势: 在低话务区经济地支持分组数据 提高业务质量 全面支持分组数据IS-95A/Bcdma2000Cdma2000高速数据的部署:高话务区 (密集城区)高速数据的要求 (14.4k 144k 307k bps)CDMA 95+ 和和1X 共存共存9090 cdma20001X 分组接入网分组接入网9191 Home IPNetworkHomeAAAMobile StationMobileClientVLRVisitedAAASS7NetworkAccess NetworkPCFR-PInterfaceFAHLRHome AccessProvider NetworkPDSNIPNetworkHome ISPPrivate NetworkVisited ProviderHome ProviderHAR-P interface A10/A11 MIP/GREcdma2000 1x的数据网络结构的数据网络结构9292 PacketDataServingNode(PDSN):PacketDataServingNode(PDSN): 桥接无线接入网（桥接无线接入网（桥接无线接入网（桥接无线接入网（Radio Access NetworkRadio Access NetworkRadio Access NetworkRadio Access Network）和公众数据网（和公众数据网（和公众数据网（和公众数据网（Packet Packet Packet Packet Data NetworkData NetworkData NetworkData Network） 终结终结终结终结PPPPPPPPPPPP会话会话会话会话 协助分组数据计费协助分组数据计费协助分组数据计费协助分组数据计费 FA FA FA FA功能，支持移动功能，支持移动功能，支持移动功能，支持移动IPIPIPIP9393 Authentication,Authorization,Authentication,Authorization,AccountingServer(AAA)AccountingServer(AAA) 鉴权鉴权鉴权鉴权Authentication of profile Authentication of profile Authentication of profile Authentication of profile informationinformationinformationinformation 授权授权授权授权AuthorizationofdataservicesAuthorizationofdataservices 计费计费计费计费CollectsbillinginformationfromCollectsbillinginformationfromPDSNPDSN9494 HomeAgent(HA)HomeAgent(HA) 维护用户登录信息，重定向分组包到维护用户登录信息，重定向分组包到维护用户登录信息，重定向分组包到维护用户登录信息，重定向分组包到PDSNPDSNPDSNPDSN 利用利用利用利用AAAAAAAAAAAA执行鉴权和认证执行鉴权和认证执行鉴权和认证执行鉴权和认证 作为可选功能作为可选功能作为可选功能作为可选功能, , , , 将数将数将数将数据包通过安全隧道据包通过安全隧道据包通过安全隧道据包通过安全隧道转发转发转发转发到到到到PDSNPDSNPDSNPDSN9595 Thank You!9696